The present invention relates to a rotary copying machine for printing a full page or for printing a line or a section of a printing form on a rotatable printing drum with a device for moistening the sheets to be printed, wherein the moistening liquid is fed to the moistening device by means of a pump with an adjustable stroke.
As a rule, sheets of different size are used in rotary copying machines depending on whether the copying machine is used for printing a full page or for printing a line or a section of a printing form on the rotatable printing drum of the machine. If printing of a full page is desired, the sheets used are usually twice the size as the sheets used for printing a line or a section of a full page. The feeding of the liquid to the means for moistening the sheet, preferably a moistening felt, has therefore to be regulated in such a manner that at each or a predetermined number of revolutions of the printing drum of the rotary copying machine a predetermined amount of liquid is pumped to the moistening felt. The necessary amount of liquid will depend on the size of the sheet to be printed so that this amount has to be changed during adjustment of the copying machine for printing a full page, a line or a section of a full page. This is accomplished according to the prior art by the operator who adjusts by means of an eccentric the piston stroke of the pump feeding the liquid. However, in this known manner of adjustment it happens often that, due to faulty operation, an adjustment of the liquid to be fed according to the size of the sheets used will either not be carried out at all or be carried out in insufficient manner so that the sheets will either be moistened too much or too little, whereby the quality of the printing will be detrimentally affected.